1. Field of Invention
The present invention relates to energy consumption evaluation for electronic device, and more particularly to embedded system in energy consumption evaluation.
2. Description of Related Art
An embedded system mainly includes embedded processor, related supporting hardware system and embedded software system. And the embedded system is an integrated “device” of hardware and software which can run independently. The embedded processor is mainly composed of a single-chip microcomputer or a microcontroller unit (MCU) and the supporting hardware may include graphics card, storage medium (such as ROM, RAM and etc.), communication equipment, IC card or credit card reading device, and etc.
The embedded system is different from a general computing system in which the embedded system does not have a large storage medium like hard disk, and utilizes Flash Memory as the storage medium. The embedded software includes underlying software which is related to hardware, e.g. operating system, graphical interface, communication protocol, database system, standardized browser, application software and etc.
Embedded system is the most widely used computing system. With the development of computer hardware technology, the performance of the embedded device becomes higher and higher. In order to keep mobility, the majorities of embedded device unable to connect to a fixed power source and usually use batteries for power supply. However, battery has limited power supply and fails to meet the ever growing computing requirements. For example, five years ago, a cell phone can be used for one week per charging while a smart phone now can be used for at most two days and has to be recharged. At the same time, the energy cost of the embedded system with active power supply has dramatically increased with the increase in energy prices. The energy supply issue becomes a key limiting factor in the development of embedded device. Since the limitations imposed by energy storage capacity of battery, the effective utilization of battery power and the extension of embedded system running time become an urgent and unavoidable issues.
Most of existing energy consumption simulation systems for embedded device simulate at the hardware level. This kind of simulation systems simulates at circuit level and the majority of which are designed by hardware developers. In other words, this type of simulation system is targeted at the hardware product of the developers only. This kind of simulation system is related to hardware platform directly so the energy consumption parameters of the device are required for simulation. In other words, the hardware has to be physical implemented. Therefore this type of existing simulation system is not suitable to simulate the non-existed devices or devices under development. In addition, this type of simulation system is not platform-independent, and it is impossible to compare results between different platforms. Besides, existing simulation systems only support hardware energy consumption simulation and fail to consider the effect of software in energy consumption. For a normal embedded device, it consumes the most energy when the device is running tasks. The energy consumption is different a lot between an idle system and a system with load charging. Furthermore, some kinds of processor, such as ARM, support multiple sets of instructions (ARM supports both 32-bit and 16-bit instructions sets), and the energy consumption level is different while running in different instruction modes (the 16 mode has a much lower energy consumption level than the 32 mode in ARM) while the switching of instruction modes is mostly caused by the task requirement. For example, the energy consumption of system has a big difference between wireless communication and computing. Accordingly, the existing simulation system can only simulate the energy consumption of hardware and fails to obtain the actual energy consumption of a running embedded system.